Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: An upstream side catalyst and a downstream side catalyst are disposed in an exhaust passage. A first oxygen sensor is disposed between these two catalysts and a second oxygen sensor is disposed downstream of the downstream side catalyst. The air-fuel ratio is forcibly oscillated and the oxygen storage capacity of the upstream side catalyst is detected. Deterioration of the upstream side catalyst is then detected based on whether this oxygen storage capacity is larger than a predetermined value. The forced oscillation of the air-fuel ratio is performed only when the oxygen storage state of the downstream side catalyst is appropriate.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: An air-fuel ratio control apparatus estimates, on the basis of an exhaust air-fuel ratio of exhaust gas flowing into an exhaust purifying catalyst unit disposed in an exhaust passage of an engine, an emission of at least one specific component contained in exhaust gas flowing out of the exhaust purifying catalyst unit. The air-fuel ratio control apparatus performs the estimation by use of a model, and controls the air-fuel ratio in such a manner that the estimation value reaches a target state. The model is previously determined in consideration of the mass balance of the specific component.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: An exhaust purification apparatus for an internal combustion engine includes a catalyst unit disposed in an exhaust passage of the engine, upstream and downstream air-fuel-ratio sensors disposed upstream and downstream, respectively, of the catalyst unit, a main-feedback controller, and a sub-feedback controller. The main-feedback controller calculates a main-feedback control quantity on the basis of an output value of the upstream air-fuel-ratio sensor and a predetermined upstream-side target value, and corrects, on the basis of the main-feedback control quantity, the quantity of fuel injected by an fuel injector.

Abstract: An exhaust gas control apparatus and an exhaust gas purification method are for an internal combustion engine provided with a first catalyst portion disposed in an exhaust passage of the internal combustion engine, and a second catalyst portion disposed in the exhaust passage downstream of the first catalyst portion. A value that changes according to at least an amount of oxygen stored in the first catalyst portion is obtained as an obtained value. An air-fuel ratio of the internal combustion engine is controlled such that the obtained value matches a target value. A value that changes according to at least an amount of oxygen stored in the second catalyst portion is calculated as a calculated value, based on at least a state of exhaust gas flowing into the second catalyst portion. The target value is changed according to the calculated value.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: A catalyst degradation determining method includes the steps of: controlling an upstream-of-catalyst air-fuel ratio occurring upstream of a first catalyst to an air-fuel ratio that is rich of a stoichiometric air-fuel ratio so that first and second catalysts store oxygen up to a maximum storage amount of oxygen. The method then includes the steps of controlling the upstream-of-catalyst air-fuel ratio to a first lean air-fuel ratio until an output of a downstream-of-first-catalyst sensor indicates a lean air-fuel ratio, and then to a second lean air-fuel ratio and that has a value that is determined in accordance with an oxidizing-reducing capability index value, until a time point when an output of a downstream-of-second-catalyst air-fuel ratio sensor indicates an air-fuel ratio that is lean.

Abstract: An air-fuel ratio control apparatus of an internal combustion engine according to the present invention is provided with oxygen storage amount estimating means, downstream exhaust air-fuel ratio detecting means, maximum oxygen storage amount estimating means, and air-fuel ratio target setting means. The oxygen storage amount estimating means estimates an oxygen storage amount of an exhaust purifying catalyst, based on a history of an oxygen adsorption/desorption amount of the exhaust purifying catalyst located on an exhaust path. The downstream exhaust air-fuel ratio detecting means is located downstream of the exhaust purifying catalyst and detects an exhaust air-fuel ratio downstream of the exhaust purifying catalyst. The maximum oxygen storage amount estimating means estimates a maximum oxygen storage amount, based on an oxygen storage amount estimate when the exhaust air-fuel ratio detected is a predetermined air-fuel ratio.

Abstract: An exhaust gas purification system comprises a NOx catalyst for absorbing the NOx in the exhaust gas when the air-fuel ratio of the influent exhaust gas is lean and purifying by reducing the absorbed NOx with a reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas turns rich, a first unit for calculating the amount of NOx absorbed per unit time in each area of the NOx catalyst when the air-fuel ratio of the exhaust gas flowing into the NOx catalyst is lean, and a second unit for calculating the total amount of NOx absorbed into the NOx catalyst by totaling the amounts of NOx calculated by the first calculation unit for the areas of the NOx catalyst.

Abstract: An exhaust purification apparatus for an internal combustion engine includes a catalyst unit disposed in an exhaust passage of the engine, upstream and downstream air-fuel-ratio sensors disposed upstream and downstream, respectively, of the catalyst unit, a main-feedback controller, and a sub-feedback controller. The main-feedback controller calculates a main-feedback control quantity on the basis of an output value of the upstream air-fuel-ratio sensor and a predetermined upstream-side target value, and corrects, on the basis of the main-feedback control quantity, the quantity of fuel injected by an fuel injector.

Abstract: A catalytic emission control apparatus of an internal combustion engine that has an engine stop mode of stopping the internal combustion engine during a run of a vehicle utilizes an oxygen absorption-storage action of an emission control catalyst disposed in an exhaust passage of the internal combustion engine. The emission control apparatus has a storage computing device that computes a storage of oxygen in the emission control catalyst, and air-fuel ratio controller performs an air-fuel ratio control of the internal combustion engine based on the storage of oxygen computed by the storage computing device. The storage computing device computes the storage of oxygen during the engine stop mode of the internal combustion engine. The air-fuel ratio controller performs the air-fuel ratio control when the internal combustion engine is restarted after the engine stop mode is discontinued, based on the storage of oxygen computed by the storage computing device during the engine stop mode.

Abstract: An air-fuel ratio control apparatus according to the present invention estimates, on the basis of an exhaust air-fuel ratio of exhaust gas flowing into an exhaust purifying catalyst unit 19 disposed in an exhaust passage 7 of an engine 1, an emission of at least one specific component contained in exhaust gas flowing out of the exhaust purifying catalyst unit. The air-fuel ratio control apparatus performs the estimation by use of a model, and controls the air-fuel ratio in such a manner that the estimation value reaches a target state. The model is previously determined in consideration of the mass balance of the specific component.

Abstract: An exhaust gas control apparatus and an exhaust gas purification method are for an internal combustion engine provided with a first catalyst portion disposed in an exhaust passage of the internal combustion engine, and a second catalyst portion disposed in the exhaust passage downstream of the first catalyst portion. A value that changes according to at least an amount of oxygen stored in the first catalyst portion is obtained as an obtained value. An air-fuel ratio of the internal combustion engine is controlled such that the obtained value matches a target value. A value that changes according to at least an amount of oxygen stored in the second catalyst portion is calculated as a calculated value, based on at least a state of exhaust gas flowing into the second catalyst portion. The target value is changed according to the calculated value.

Abstract: A catalyst degradation determining method is for use with an emission control apparatus of an internal combustion engine that includes a catalyst disposed in an exhaust passage of the internal combustion engine, and a downstream-of-catalyst air-fuel ratio sensor disposed in the exhaust passage downstream of the catalyst. The method includes the steps of: acquiring an oxidizing-reducing capability index value that changes in accordance with a degree of an oxidizing-reducing capability of the catalyst; controlling an upstream-of-catalyst air-fuel ratio occurring upstream of the catalyst to an air-fuel ratio that is lean of a stoichiometric air-fuel ratio so that the catalyst stores oxygen in the catalyst up to a maximum storage amount of oxygen.

Abstract: In a control device, in a control device of an internal combustion engine provided with an internal combustion engine main body mounted to a vehicle and a heater operating on the basis of an output from a specific sensor given as a trigger at least before the internal combustion engine main body starts, whether or not the heater is operated before the start is stored, and it is judged that the sensor has failed when operation of the heater is not stored.

Abstract: An exhaust gas purification system comprises a NOx catalyst for absorbing the NOx in the exhaust gas when the air-fuel ratio of the influent exhaust gas is lean and purifying by reducing the absorbed NOx with a reducing agent in the exhaust gas when the air-fuel ratio of the exhaust gas turns rich, a first unit for calculating the amount of NOx absorbed per unit time in each area of the NOx catalyst when the air-fuel ratio of the exhaust gas flowing into the NOx catalyst is lean, and a second unit for calculating the total amount of NOx absorbed into the NOx catalyst by totaling the amounts of NOx calculated by the first calculation unit for the areas of the NOx catalyst.